Population structure of a native and an alien species of snail in an urban area of the Atlantic Rainforest

Native Megalobulimus paranaguensis was identified on Brazil’s Ilha Porchat promontory, an area that Achatina fulica commonly populates. The population structures of these species were investigated for interactions. Spatial distribution, niche overlap and mark–recapture analysis were conducted. The outer lip of M. paranaguensis and environmental variables were measured. One and two abundance peaks were observed for A. fulica and M. paranaguensis, respectively. Survivorship was higher in A. fulica. Distribution was aggregate for M. paranaguensis, whereas for A. fulica it varied from random to aggregate. Both species aggregate as abundance increases. The lifespan of M. paranaguensis in this location is shorter than its lifespan in a nearby location. Achatina fulica was affected by soil temperature and humidity; M. paranaguensis was influenced by humidity. Niche overlap was random. The results show that M. paranaguensis can keep its natural activity and abundance in the presence of A. fulica, but environmental degradation impacts M. paranaguensis and should be evaluated.     

Reproductive phenology and flower visitors' guild of Canistropsis microps (Bromeliaceae) in an Atlantic Rainforest of southeastern Brazil

The reproductive phenology and guild of the floral visitors of Canistropsis microps in an Atlantic Forest area in Ilha Grande, RJ were studied for 4 years. The rates of flowering, fruiting and mortality were related to air temperature, rainfall and photoperiod. To register the flower visitors, observations were carried out for 5 days in each reproductive season. The flowering and fruiting occurred in the rainy season and were positively related to the studied climatic variables, whereas the highest mortality rates occurred in the dry season and were negatively related to the climatic variables. The guild of floral visitors of C. microps was composed of Hymenoptera, characterizing the species as a melittophilous plant. These results indicate that the rainy season presents more favourable conditions for investment in sexual reproduction, besides being the period in which potential pollinators have larger population densities and a longer period of activity.     

Microdistribution of juveniles and adults of the mud crab Panopeus americanus (Brachyura,Panopeidae) in a remnant mangrove area in the southwest Atlantic

The distribution and density of a population of the narrowback mud crab Panopeus americanus were evaluated, with emphasis on the different developmental stages (juveniles and adults) and sexes. Specimens were collected in a remnant human‐impacted mangrove at Araçá on the northern coast of São Paulo, Brazil, at two‐month intervals from January through July 2006, using 1 m×1 m sample plots randomly distributed in the intertidal zone. The population was abundant, with a mean density of 14.3±9.3 individuals/m². Larger individuals were more abundant in the upper and middle intertidal zones, whereas smaller crabs were predominant in the lower intertidal and thus remained submerged longer. Males and juveniles were homogeneously distributed. Females preferred regions farther from the waterline. A clustered distribution pattern suggested gregarious behaviour and settling of juveniles in the vicinity of the adults' habitats, in an adaptive process as a function of tidal rhythms.     

Co-existence of myxomycetes and beetles in an Atlantic Rainforest remnant of Pernambuco,Brazil, with emphasis on staphylinids (Coleoptera: Staphylinidae)

The relationship between myxomycetes and insects was investigated in a fragment of the Brazilian Atlantic Rainforest located in the city of Recife, Pernambuco, north-eastern Brazil. Sixteen excursions into the Dois Irmãos State Ecological Reserve (7°55′43′′ to 8°09′17′′ S, 34°52′05′′ to 35°00′59′′ W, 387.4 ha) were carried out during different seasons between August 2005 and August 2007 for observations and collections of myxomycetes and insects on decomposing trunks and leaf litter. A total of 196 specimens of myxomycetes was obtained, representing 31 species, 16 genera and six families. Baeocera sp. (Coleoptera, Staphylinidae) individuals predominated (86%) in the sample, found on the sporocarps of four species of Trichiales (Arcyria cinerea, Arcyria denudata, Hemitrichia calyculata, Hemitrichia serpula) and two species of Liceales (Lycogala epidendrum, Tubulifera microsperma). No preference was observed for type of sporocarp. No seasonal influence was found for the establishment of these associations, recorded for the first time in this forest environment.     

Estimating population features of the anomuran crab Petrolisthes armatus (Porcellanidae) in a remaining and impacted mangrove area of the western Atlantic

This study evaluated biological aspects of Petrolisthes armatus inhabiting a remaining but disturbed mangrove area of Brazil. Samples were taken from March 2005 to July 2006, during low tide in the rocky-shore region. The size frequency distribution for all the individuals collected was bimodal. The sex ratio obtained was not different from 1:1, and the population was classified as standard. A higher reproductive ratio and earlier ovigerous conditions were found in relation to another southern population; these can be hypothesized as adaptations to life in a stressed environment. Even though the population living in Araçá has been subject to an environment frequently disturbed by human-produced pollutants, our results show no sign of negative effects on reproductive stages, recruits or members of the population in general. The population profiles of P. armatus show some peculiarities when compared to other populations inhabiting non disturbed environments.     

Responses of pink shrimp Farfantepenaeus brasiliensis (Latreille, 1817) (Penaeoidea) to physico-chemical parameters in a marine protected area: changes in abundance and distribution after 20 years

ABSTRACT

This study analysed the influence of temperature, salinity and sediment texture on the distribution of pink shrimp juveniles (Farfantepenaeus brasiliensis) over a 20-year period. The shrimps were sampled monthly in Fortaleza Bay, north coast of São Paulo, Brazil, in November 1988–October 1989 (period 1) and then 20 years later in November 2008–October 2009 (period 2). In period 1 we captured 80 juveniles whereas in period 2 we captured 226. The abundance and distribution of F. brasiliensis seemed to be modulated by temperature and sediment texture, along with the fishing activity. The management strategies established between the samplings might have been responsible for the higher abundance of juveniles seen during period 2. The strategies included the limitation of fishing effort, regulation of fishing equipment and the establishment of environmental protection areas and temporary fishing ban.